Our newer servers don’t have screen – and you cannot install it – so I’ve had to start using tmux:

# list running sessions
tmux ls

# Start a new session or reattach to an existing session named LJR
tmux new-session -A -s LJR

# In session, detach
ctrl+b d Detach

# attach to an existing session named LJR
tmux attach-session -t LJR